JP2011242610A - Photographic lens, and inspection device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographic lens having minimal aberration fluctuation caused by magnification fluctuation, and having high optical performance, and to provide an inspection device including the photographic lens.SOLUTION: A photographic lens includes in order from an object side: a first lens group G1 having positive refractive power; a second lens group G2 having positive refractive power; wherein the first lens group includes a first-a lens group G1a having positive refractive power, a diaphragm SP and a first-b lens group having positive refractive power. The first-a lens group includes a positive lens L1 with a convex surface directed to the object side, a positive lens L2 with a convex surface directed to the object side, and a negative lens L3 with a strong concave surface directed to the image side. The first-b lens group includes a negative meniscus lens L4 with a concave surface directed to the object side, and a positive lens L5. The second lens group includes a biconcave lens L6 and a positive meniscus lens L7 with a convex surface directed to the image side. In the case of focusing from an object at infinity to an object at a close distance, the first lens group and the second lens group move toward the object side by different moving amount respectively, so as to increase a distance between the first lens group and the second lens group. The photographic lens satisfies appropriately set conditions.

Description

  The present invention relates to a photographic lens and an inspection apparatus including the photographic lens.

  2. Description of the Related Art In recent years, taking lenses used for visual inspection of sheets, printed surfaces, and the like have been required to have higher performance with respect to taking lenses to be used as inspection objects and image sensors have become higher in definition. Specifically, there is a demand for an increase in image size, a curvature of field, a significant reduction in distortion, and the like accompanying an increase in the size of the image sensor, including an improvement in resolution. In addition, the sizes of inspection objects are diversified, and various appearance inspection apparatuses corresponding to the sizes are required. In order to meet such a demand, a photographic lens capable of zooming is known (see, for example, Patent Documents 1 and 2). The photographic lens described in Patent Document 1 is a lens in which the curvature of field and the distortion are well corrected within the magnification variation range. The photographic lens described in Patent Document 2 is a lens in which axial chromatic aberration and chromatic aberration of magnification are well corrected within a magnification variation range.

JP 2000-284172 A JP 2005-189727 A

  However, in the conventional photographing lens, it is difficult to suppress the variation in spherical aberration and coma due to the variation in magnification, so that there is a problem that the resolution of the image deteriorates depending on the magnification used.

  The present invention has been made in view of such problems, and various aberrations such as spherical aberration, axial chromatic aberration, and lateral chromatic aberration are satisfactorily corrected within a usable magnification range while suppressing the number of constituent lenses. An object of the present invention is to provide a photographic lens having a small aberration variation due to the variation and having high optical performance from the center to the periphery of an image, and an inspection apparatus including the photographic lens.

  In order to achieve such an object, the present invention provides a photographing lens having a first lens group having a positive refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side. The first lens group includes a 1a lens group having a positive refractive power, arranged in order from the object side, a stop, and a 1b lens group having a positive refractive power, and the 1a lens group includes: A positive lens having a convex surface facing the object side, a positive lens having a convex surface facing the object side, and a negative lens having a strong concave surface facing the image side, arranged in order from the object side, A negative meniscus lens having a concave surface facing the object side, and a positive lens arranged in order from the object side, and the second lens group has a biconcave lens arranged in order from the object side, and a convex surface on the image side. With a positive meniscus lens to focus on objects from infinity to short distances The first lens group and the second lens group move toward the object side along the optical axis with different movement amounts so that the distance between the first lens group and the second lens group increases. When the radius of curvature on the image side of the biconcave lens constituting the second lens group is Rm, and the radius of curvature on the object side of the positive meniscus lens constituting the second lens group is Rp, the following formula | (Rm + Rp) /(Rm−Rp)|<0.25 is satisfied.

  In the photographic lens of the present invention, the refractive power at the d-line (wavelength 587.56 nm) of the second lens group is Φ2, and it is formed between the biconcave lens and the positive meniscus lens constituting the second lens group. When the refractive power at the d-line of the air lens is Φ2A, it is preferable to satisfy the following condition: −0.65 <Φ2 / Φ2A <−0.08.

  In the photographing lens of the present invention, it is preferable that the positive lens constituting the 1b lens group is a positive meniscus lens having a convex surface facing the image side.

  In the photographic lens of the present invention, the refractive power of the entire photographic lens system at the d-line when focusing on an object at infinity is Φi, the refractive power of the first lens group at the d-line is Φ1, When the refractive power at the d-line of the second lens group is Φ2, it is preferable to satisfy the following conditions: 0.7 <Φ1 / Φi <1.2 and 0.07 <Φ2 / Φ1 <0.37.

  In the photographic lens of the present invention, when the refractive power at the d-line of the 1b lens group is Φ1b and the refractive power at the d-line of the negative meniscus lens constituting the 1b lens group is Φ1m, It is preferable that the condition of 1.0 <Φ1b / Φ1m <−0.4 is satisfied.

  In the photographic lens of the present invention, the refractive power at the d-line of the entire photographic lens system when focusing on a short-distance object is Φn, and the focusing is performed from an infinite object to a short-distance object. When the change in the distance between the first lens group and the second lens group is ΔD, it is preferable to satisfy the following condition: | (Φn−Φi) / ΔD | <0.35.

  The inspection apparatus of the present invention includes the above-described photographing lens that forms an image of light from an object at a predetermined position.

  According to the present invention, various aberrations such as spherical aberration, axial chromatic aberration, and lateral chromatic aberration are satisfactorily corrected within the working magnification range while suppressing the number of constituent lenses, and further, the variation in aberration due to the variation in magnification is small and the center of the image is reduced. It is possible to provide an imaging lens having high optical performance from the periphery to the periphery and an inspection apparatus including the imaging lens.

FIG. 3 is a cross-sectional view illustrating a configuration of a photographic lens according to a first example and a state of movement of each lens unit in a focus change from an infinitely focused state to a short-distance focused state. FIG. 6 is a diagram illustrating various aberrations when focusing on an object at infinity in the photographing lens according to the first example. FIG. 7 is a diagram illustrating various aberrations when focusing on a short-distance object in the photographing lens according to the first example. Sectional drawing which shows the mode of a structure of the photographic lens which concerns on 2nd Example, and the mode of a movement of each lens group in the focus change from an infinite focus state to a short distance focus state is shown. FIG. 10 is a diagram illustrating various aberrations when focusing on an object at infinity in the photographing lens according to Example 2. FIG. 10 is a diagram illustrating various aberrations when focusing on a short-distance object in the photographing lens according to Example 2. Sectional drawing which shows the mode of the structure of the imaging lens which concerns on 3rd Example, and the mode of a movement of each lens group in the focus change from an infinite focus state to a short-distance focus state is shown. FIG. 12 is a diagram illustrating various aberrations when focusing on an object at infinity in the photographing lens according to the third example. FIG. 11 is a diagram illustrating various aberrations when focusing on a short-distance object in the photographing lens according to the third example. It is a principal part schematic diagram of the inspection apparatus using the photographic lens concerning the present invention.

  Hereinafter, the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the photographing lens according to the present embodiment includes a first lens group G1 having a positive refractive power and a second lens group G2 having a positive refractive power, which are arranged in order from the object side. . The first lens group G1 includes, in order from the object side, a first a lens group G1a having a positive refractive power, a stop SP, and a first b lens group G1b having a positive refractive power. The group G1a includes, in order from the object side, a positive lens L1 having a convex surface facing the object side, a positive lens L2 having a convex surface facing the object side, and a negative lens L3 having a strong concave surface facing the image side. The first-b lens group G1b includes a negative meniscus lens L4 having a concave surface facing the object side and a positive meniscus lens L5 having a convex surface facing the image side, which are arranged in order from the object side.

  As described above, the first lens group G1 of the photographing lens according to the present embodiment is a substantially xenoter type lens. The xenoter lens has high refractive power symmetry before and after the stop SP, and correction of distortion aberration, lateral chromatic aberration, and the like is easy due to the symmetry. Further, the coma aberration can be favorably corrected up to the periphery of the image by the negative meniscus lens L4 disposed behind the stop SP.

  The second lens group G2 of the photographing lens according to the present embodiment includes a biconcave lens L6 and a positive meniscus lens L7 having a convex surface facing the image side, which are arranged in order from the object side. Astigmatism and lateral chromatic aberration can be corrected by forming an air lens having negative refractive power with the positive meniscus lens L7. And by this structure, the effect of conditional expression (1) mentioned later can be exhibited to the maximum.

  Furthermore, the photographing lens according to the present embodiment has the first lens group so that the distance between the first lens group G1 and the second lens group G2 increases when focusing from an object at infinity to an object at a short distance. By moving the G1 and the second lens group G2 toward the object side along the optical axis with different movement amounts, it becomes possible to suppress fluctuations in various aberrations within the use magnification range.

  In the photographic lens according to this embodiment having the above-described configuration, the radius of curvature of the image side of the biconcave lens L6 constituting the second lens group G2 is Rm, and the positive meniscus lens L7 constituting the second lens group G2 is used. When the radius of curvature on the object side is Rp, the following conditional expression (1) is satisfied.

  | (Rm + Rp) / (Rm−Rp) | <0.25 (1)

  Conditional expression (1) is an appropriate range between the radius of curvature on the image side of the biconcave lens L6 constituting the second lens group G2 and the radius of curvature on the object side of the positive meniscus lens L7 constituting the second lens group G2. Is shown. If the upper limit of conditional expression (1) is exceeded, the air lens formed in the second lens group G2 by these lenses L6 and L7 cannot take an appropriate shape, and the curvature of the meridional image plane becomes large. Thus, correction of astigmatism becomes difficult. In addition, since the incident angle and the exit angle of off-axis rays with respect to the air lens are greatly deviated from appropriate angles, coma increases and correction is difficult.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.20.

  In the photographic lens according to the present embodiment, the refractive power at the d-line of the second lens group G2 is Φ2, and the air formed between the biconcave lens L6 and the positive meniscus lens L7 constituting the second lens group G2. When the refractive power at the d-line of the lens is Φ2A, it is preferable that the following conditional expression (2) is satisfied.

  −0.65 <Φ2 / Φ2A <−0.08 (2)

  Conditional expression (2) represents an appropriate range between the refractive power of the second lens group G2 and the refractive power of the air lens formed in the second lens group G2. If the lower limit value of conditional expression (2) is not reached, the Petzval sum in the second lens group G2 becomes too large, and the field curvature becomes too large, making it difficult to correct well. If the upper limit value of the conditional expression (2) is exceeded, the power balance of the second lens group G2 is greatly lost, large distortion occurs in the positive direction, and chromatic aberration of magnification also increases. It becomes difficult to correct.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to −0.56. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to −0.11.

  In the photographic lens according to the present embodiment, the refractive power at the d-line of the entire photographic lens system when focusing on an object at infinity is Φi, the refractive power at the d-line of the first lens group G1 is Φ1, When the refractive power of the second lens group G2 at the d-line is Φ2, it is preferable that the following conditional expressions (3) and (4) are satisfied.

0.7 <Φ1 / Φi <1.2 (3)
0.07 <Φ2 / Φ1 <0.37 (4)

  Conditional expression (3) shows an appropriate range between the refractive power of the entire photographing lens system and the refractive power of the first lens group G1 when focusing on an object at infinity. If the lower limit of conditional expression (3) is not reached, the refractive power of the first lens group G1 becomes relatively weak, the spherical aberration becomes excessively large, and the size of the first lens group G1 is increased. . If the upper limit value of conditional expression (3) is exceeded, the refractive power of the first lens group G1 becomes relatively strong, and a large distortion occurs in the negative direction, making correction difficult.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.8. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 1.1.

  Conditional expression (4) shows an appropriate range of the refractive power of the first lens group G1 and the refractive power of the second lens group G2 when focusing on an object at infinity. If the lower limit of conditional expression (4) is not reached, the refractive power of the second lens group G2 becomes relatively weak, the lateral chromatic aberration increases, and when focusing from an object at infinity to a near object is performed. Since the change in the distance between the first lens group G1 and the second lens group G2 must be increased, the overall size of the photographing lens is increased. If the upper limit of conditional expression (4) is exceeded, the symmetry of the refractive power before and after the stop SP is greatly lost, making it difficult to correct distortion and lateral chromatic aberration.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.09. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.31.

  In the photographing lens according to the present embodiment, when the refractive power at the d line of the first b lens group G1b is Φ1b and the refractive power at the d line of the negative meniscus lens L4 constituting the first b lens group G1b is Φ1m, It is preferable that the following conditional expression (5) is satisfied.

  −1.0 <Φ1b / Φ1m <−0.4 (5)

  Conditional expression (5) shows an appropriate range between the refractive power of the first lens group G1b and the refractive power of the negative meniscus lens L4 constituting the first lens group G1b. This is an important condition for correction. If the lower limit of conditional expression (5) is not reached, the angle of the light beam emitted from the negative meniscus lens L4 with respect to the optical axis decreases, and the sine condition violation amount increases in the negative direction. This makes it difficult to correct coma. If the upper limit of conditional expression (5) is exceeded, the angle of the light beam emitted from the negative meniscus lens L4 with respect to the optical axis increases, and the sine condition violation amount increases in the positive direction. This makes it difficult to correct coma.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to −0.9. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to −0.5.

  In the photographic lens according to the present embodiment, the refractive power at the d-line of the entire photographic lens system when focusing on a short-distance object is Φn, and the focusing is performed from an infinite object to a short-distance object. When the change in the distance between the first lens group G1 and the second lens group G2 is ΔD, the following conditional expression (6) is preferably satisfied.

  | (Φn−Φi) / ΔD | <0.35 (6)

  Conditional expression (6) is an appropriate range between the refractive power of the entire photographic lens system at the time of focusing and the change in the distance between the first lens group G1 and the second lens group G2 at the time of focusing. Is shown. If the upper limit of conditional expression (6) is exceeded, it is difficult to correct curvature of field and coma when focusing, and it becomes difficult to obtain good optical performance within the magnification range.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 0.24.

  In the photographic lens according to the present embodiment, the lens system is composed of two movable groups (that is, the first lens group G1 and the second lens group G2), but other lens groups are provided between the lens groups. Or another lens group can be added adjacent to the image side or the object side of the lens system.

  Next, an inspection apparatus provided with the photographic lens having the above configuration will be described with reference to FIG. This inspection apparatus images, for example, an inspection object such as an FPD (flat panel display), a printed circuit board, an electronic component, a sheet, or the like through the imaging lens having the above-described configuration, and based on the obtained image, It is to inspect for defects. Specifically, as illustrated in FIG. 10, the inspection apparatus 1 includes a photographic lens having the above-described configuration that forms an image of the inspection object 10 on the inspection object 10 and an image sensor 11 made of, for example, a CCD or a CMOS. 12, an image processing device 13, and a monitor 14. In the image processing device 13, predetermined signal processing is performed on the input image data or the electrical signal from the image sensor 11, the defect of the photographed inspection object 10 is detected, and the position thereof can be specified. . The acquired image data can be output via the monitor 14. In addition, although the specific example of the test object 10 and the image pick-up element 11 was described, this invention is not limited to these specific examples.

  As described above, in order to make the present invention easy to understand, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

  Hereinafter, each example according to the present embodiment will be described with reference to the drawings. 1, 4, and 7 are cross-sectional views illustrating the configuration of the photographic lens according to each embodiment and the movement of each lens group in the focus change from the infinite focus state to the short distance focus state. It is. As described above, the photographic lenses according to the respective examples are arranged in order from the object side, and have a first lens group G1 (first to fifth lens components L1 to L5) having positive refractive power and positive refraction. The first lens group G1 includes a first lens group G1a having positive refractive power and arranged in order from the object side. The second lens group G2 (sixth and seventh lens components L6 and L7) having power The aperture stop SP and the first lens group G1b having positive refractive power, and the second lens group G2 are arranged in order from the object side, a sixth lens component L6 that is a biconcave lens, and a convex surface on the image side The first lens group G1 and the second lens group G2 move differently when focusing from an infinite object to a short-distance object. The first lens unit moves to the object side along the optical axis with respect to the image plane by the amount 1 and the distance between the second lens group G2 is changed so as to increase.

  Tables 1 to 3 are shown below, but these are tables of specifications in the first to third examples. In [Overall specifications], f is the focal length at infinity focusing on the d-line of the entire photographic lens system, β is the magnification of the photographic lens at the d-line, Fno is the F-number at the d-line, and 2ω is the image. The angle indicates Y and the image height. In [Lens data], the surface number is the order of the lens surfaces from the object side along the direction in which the light beam travels (the 0th surface corresponds to the object surface), r is the radius of curvature corresponding to each surface number, d Is the lens thickness on the optical axis corresponding to each surface number and the air interval (the value described on the 0th surface corresponds to the air interval from the object surface to the first surface), and nd is the glass material corresponding to each surface number. The refractive index of the d-line, and νd, the Abbe number based on the d-line of the glass material corresponding to each surface number. The curvature radius “∞” indicates a plane or an opening. The description of the refractive index “1.00000” of air is omitted.

  In the table, in [Variable interval data at the time of focusing], f is the focal length at the time of focusing on infinity in the d-line of the entire taking lens system, β is the magnification of the taking lens at the d-line, and D0 is The air space from the object surface to the first surface, Di (where i is an integer) is the variable space between the i-th surface and the (i + 1) -th surface, and Bf is the back focus. In [Group Data], G is the group number, the first surface of the group is the surface number of the most object side of each group, the group focal length is the focal length (d-line) of each group, and the lens configuration length is the most object of each group The distance on the optical axis from the lens surface on the side to the lens surface closest to the image side is shown. In [Conditional Expression], the conditional expressions (1) to (6) and values corresponding thereto are shown.

  In the table, “mm” is generally used as the focal length f, radius of curvature r, surface interval d, and other length units. However, since the same optical performance can be obtained even if the optical system is proportionally enlarged or reduced, the unit is not limited to “mm”, and other appropriate units can be used.

  The description of the above table is the same in all embodiments, and the description is omitted.

(First embodiment)
The taking lens according to the first embodiment will be described with reference to FIGS. As shown in FIG. 1, in the photographing lens according to the first example, the first-a lens group G1a is arranged in order from the object side, and a positive meniscus lens L1 having a convex surface facing the object side, and a convex surface facing the object side. The positive meniscus lens L2 and a cemented lens L23 of a negative meniscus lens L3 having a concave surface facing the image side. The 1b lens group G1b is composed of a negative meniscus lens L4 having a concave surface facing the object side and a positive meniscus lens L5 having a convex surface facing the image side, which are arranged in order from the object side. The second lens group G2 includes a biconcave lens L6 arranged in order from the object side, and a positive meniscus lens L7 having a convex surface directed to the image side.

  Table 1 below shows the values of each item in the first embodiment. The surface numbers 1 to 14 in Table 1 correspond to the surfaces 1 to 14 shown in FIG.

(Table 1)
[Overall specifications]
f = 1.00
Fno = 4.00
2ω = 50.02 °
Y = 0.47

[Lens data]
Surface number r d nd νd
0 D0
1 0.62382 0.05246 1.65160 58.6
2 0.94840 0.01786
3 0.28624 0.09488 1.72916 54.6
4 2.10459 0.02009 1.59551 39.2
5 0.20342 0.11162
6 ∞ 0.13060 (Aperture SP)
7 -0.18958 0.02567 1.59551 39.2
8 -0.31717 0.01005
9 -0.97941 0.06697 1.72916 54.6
10 -0.31379 D10
11 -2.26623 0.01898 1.67270 32.2
12 2.26623 0.01882
13 -3.27852 0.06362 1.65160 58.6
14 -0.65048 Bf

[Variable interval data at the time of focusing]
Infinity Close distance f, β 1.00 -0.7
D0 ∞ 2.03271
D10 0.00558 0.14620
Bf 0.66541 1.27582

[Group data]
Group number Group first surface Group focal length Lens construction length G1 1 1.14 0.53020
G2 7 3.99 0.10142

[Conditional expression]
Rm = 0.441
Rp = -0.305
Φ2 = 0.251
Φ2A = -0.497
Φ1 = 0.878
Φi = 1.000
Φ1b = 0.685
Φ1m = -1.169
Φn = 0.969
ΔD = 0.141

Conditional expression (1) | (Rm + Rp) / (Rm−Rp) | = 0.18
Conditional expression (2) Φ2 / Φ2A = -0.51
Conditional expression (3) Φ1 / Φi = 0.88
Conditional expression (4) Φ2 / Φ1 = 0.29
Conditional expression (5) Φ1b / Φ1m = -0.59
Conditional expression (6) | (Φn−Φi) /ΔD|=0.22

  From the table of specifications shown in Table 1, it can be seen that the photographic lens according to Example 1 satisfies all the conditional expressions (1) to (6).

  FIG. 2 is a diagram of various aberrations (specifically, spherical aberration diagram, astigmatism diagram, distortion aberration diagram, magnification chromatic aberration diagram, and magnification aberration diagram) of the taking lens according to the first example when focusing on an object at infinity. (Coma aberration diagram). FIG. 3 is a diagram showing various aberrations (specifically, spherical aberration diagram, astigmatism diagram, distortion aberration diagram, chromatic aberration of magnification) of the taking lens according to the first example when focusing on a short distance object. Figure and coma aberration diagram). In each aberration diagram, d is d-line (wavelength 587.56 nm), g is g-line (wavelength 435.83 nm), C is C-line (wavelength 656.27 nm), and F is various aberrations with respect to F-line (wavelength 486.13 nm). Y represents the image height. In the spherical aberration diagram, the dotted line represents the sine condition violation amount, and the solid line represents the spherical aberration. In the astigmatism diagram, the dotted line indicates the meridional image plane, and the solid line indicates the sagittal image plane. The explanation of the above aberration diagrams is the same in the other examples, and the explanation is omitted.

  As is clear from each aberration diagram, the imaging lens according to the first example has a small variation in aberration in the magnification range from an object at infinity to an object at a close distance, and various aberrations are well corrected over the entire image. I understand that.

(Second embodiment)
A second embodiment will be described with reference to FIGS. 4 to 6 and Table 2. FIG. As shown in FIG. 4, in the photographing lens according to the second example, the 1a lens group G1a is arranged in order from the object side, and is a positive meniscus lens L1 having a convex surface facing the object side, and a convex surface facing the object side. The positive meniscus lens L2 and a cemented lens L23 of a negative meniscus lens L3 having a concave surface facing the image side. The 1b lens group G1b is composed of a negative meniscus lens L4 having a concave surface facing the object side and a positive meniscus lens L5 having a convex surface facing the image side, which are arranged in order from the object side. The second lens group G2 includes a biconcave lens L6 arranged in order from the object side, and a positive meniscus lens L7 having a convex surface directed to the image side.

  Table 2 below shows the values of each item in the second embodiment. The surface numbers 1 to 14 in Table 2 correspond to the surfaces 1 to 14 shown in FIG.

(Table 2)
[Overall specifications]
f = 1.00
Fno = 4.00
2ω = 50.00 °
Y = 0.47

[Lens data]
Surface number r d nd νd
0 D0
1 0.53167 0.04400 1.74320 49.3
2 0.75003 0.00700
3 0.26551 0.08500 1.71300 53.9
4 2.55609 0.01600 1.59551 39.2
5 0.18201 0.09800
6 ∞ 0.12400 (Aperture SP)
7 -0.17539 0.02300 1.59551 39.2
8 -0.26509 0.00300
9 -1.03827 0.06600 1.61800 63.4
10 -0.27001 D10
11 -2.19293 0.01700 1.74950 35.3
12 2.19293 0.01850
13 -1.77295 0.04900 1.74320 49.3
14 -0.64658 Bf

[Variable interval data at the time of focusing]
Infinity Close distance f, β 1.00 -0.7
D0 ∞ 2.08374
D10 0.00500 0.15200
Bf 0.71825 1.28460

[Group data]
Group number Group first surface Group focal length Lens construction length G1 1 1.02 0.46600
G2 7 10.74 0.08450

[Conditional expression]
Rm = 0.456
Rp = -0.564
Φ2 = 0.093
Φ2A = -0.764
Φ1 = 0.980
Φi = 1.000
Φ1b = 0.898
Φ1m = -1.039
Φn = 0.987
ΔD = 0.147

Conditional expression (1) | (Rm + Rp) / (Rm−Rp) | = 0.11
Conditional expression (2) Φ2 / Φ2A = -0.12
Conditional expression (3) Φ1 / Φi = 0.98
Conditional expression (4) Φ2 / Φ1 = 0.09
Conditional expression (5) Φ1b / Φ1m = -0.86
Conditional expression (6) | (Φn−Φi) /ΔD|=0.09

  From the table of specifications shown in Table 2, it can be seen that the photographic lens according to Example 2 satisfies all the conditional expressions (1) to (6).

  FIG. 5 is a diagram illustrating various aberrations of the photographic lens according to Example 2 when focusing on an object at infinity. FIG. 6 is a diagram illustrating various aberrations of the photographing lens according to Example 2 when focusing on a short-distance object. As is apparent from each aberration diagram, the imaging lens according to the second example has a small variation in aberration in the magnification range from an object at infinity to an object at a close distance, and various aberrations are well corrected throughout the entire image. I understand that.

(Third embodiment)
A third embodiment will be described with reference to FIGS. As shown in FIG. 7, in the photographing lens according to the third example, the 1a lens group G1a includes a positive meniscus lens L1 arranged in order from the object side and having a convex surface facing the object side, and a convex surface facing the object side. A positive meniscus lens L2 and a negative meniscus lens L3 having a concave surface facing the image side. The 1b lens group G1b is composed of a negative meniscus lens L4 having a concave surface facing the object side and a positive meniscus lens L5 having a convex surface facing the image side, which are arranged in order from the object side. The second lens group G2 includes a biconcave lens L6 arranged in order from the object side, and a positive meniscus lens L7 having a convex surface directed to the image side.

  Table 3 below shows values of various specifications in the third example. In addition, the surface numbers 1-15 in Table 3 respond | correspond to the surfaces 1-15 shown in FIG.

(Table 3)
[Overall specifications]
f = 1.00
Fno = 4.00
2ω = 50.02 °
Y = 0.47

[Lens data]
Surface number r d nd νd
0 D0
1 0.40604 0.05960 1.81600 46.6
2 1.00505 0.00202
3 0.27963 0.04445 1.77250 49.6
4 0.32514 0.02626
5 0.43126 0.01717 1.75520 27.5
6 0.19977 0.11415
7 ∞ 0.12627 (Aperture SP)
8 -0.20497 0.01616 1.60342 38.0
9 -0.34204 0.01212
10 -0.98489 0.05758 1.77250 49.6
11 -0.30073 D11
12 -3.82920 0.01616 1.75520 27.5
13 2.37480 0.01699
14 -1.72091 0.03535 1.77250 49.6
15 -0.69694 Bf

[Variable interval data at the time of focusing]
Infinity Close distance f, β 1.00 -1.0
D0 ∞ 1.65008
D11 0.00500 0.22431
Bf 0.71825 1.54294

[Group data]
Group number Group first surface Group focal length Lens construction length G1 1 1.10 0.47578
G2 8 5.81 0.06850

[Conditional expression]
Rm = 0.421
Rp = -0.581
Φ2 = 0.172
Φ2A = -0.769
Φ1 = 0.910
Φi = 1.000
Φ1b = 0.897
Φ1m = -1.127
Φn = 0.965
ΔD = 0.220

Conditional expression (1) | (Rm + Rp) / (Rm−Rp) | = 0.16
Conditional expression (2) Φ2 / Φ2A = -0.22
Conditional expression (3) Φ1 / Φi = 0.91
Conditional expression (4) Φ2 / Φ1 = 0.19
Conditional expression (5) Φ1b / Φ1m = -0.80
Conditional expression (6) | (Φn−Φi) /ΔD|=0.16

  From the table of specifications shown in Table 3, it can be seen that the photographic lens according to the third example satisfies all the conditional expressions (1) to (6).

  FIG. 8 is a diagram illustrating various aberrations of the photographic lens according to Example 3 when focusing on an object at infinity. FIG. 9 is a diagram illustrating various aberrations when the photographing lens according to Example 3 is focused on a short-distance object. As is clear from each aberration diagram, the imaging lens according to the third example has a small variation in aberration in the magnification range from an object at infinity to an object at a short distance, and various aberrations are corrected well over the entire image. I understand that.

G1 1st lens group G1a 1a lens group G1b 1b lens group G2 2nd lens group SP Aperture Li i-th lens from object side Lij Joint lens consisting of i-th lens and j-th lens from object side 1 Inspection device DESCRIPTION OF SYMBOLS 10 Inspection object 11 Image sensor 12 Shooting lens 13 Image processing apparatus 14 Monitor

Claims (7)

In a photographic lens having a first lens group having a positive refractive power and a second lens group having a positive refractive power, arranged in order from the object side,
The first lens group includes, in order from the object side, a 1a lens group having a positive refractive power, a stop, and a 1b lens group having a positive refractive power,
The first-a lens group includes a positive lens having a convex surface facing the object side, a positive lens having a convex surface facing the object side, and a negative lens having a strong concave surface facing the image side, which are arranged in order from the object side. ,
The first b lens group includes a negative meniscus lens arranged in order from the object side and having a concave surface facing the object side, and a positive lens.
The second lens group includes a biconcave lens arranged in order from the object side, and a positive meniscus lens having a convex surface facing the image side,
When focusing from an object at infinity to an object at a short distance, the first lens group and the second lens group move differently so that the distance between the first lens group and the second lens group increases. To move to the object side along the optical axis,
When the radius of curvature on the image side of the biconcave lens constituting the second lens group is Rm, and the radius of curvature on the object side of the positive meniscus lens constituting the second lens group is Rp, the following expression | (Rm + Rp) / (Rm−Rp) | <0.25
A photographic lens characterized by satisfying the above conditions. The refractive power at the d-line (wavelength 587.56 nm) of the second lens group is Φ2, and the refractive power at the d-line of the air lens formed between the biconcave lens and the positive meniscus lens constituting the second lens group. When Φ2A, the following formula −0.65 <Φ2 / Φ2A <−0.08
The photographic lens according to claim 1, wherein the following condition is satisfied.   3. The photographic lens according to claim 1, wherein the positive lens constituting the first lens group is a positive meniscus lens having a convex surface facing the image side. The refractive power at the d-line of the entire photographing lens system when focusing on an object at infinity is Φi, the refractive power at the d-line of the first lens group is Φ1, and the refraction at the d-line of the second lens group. When the force is Φ2, the following expression 0.7 <Φ1 / Φi <1.2
0.07 <Φ2 / Φ1 <0.37
The photographic lens according to claim 1, wherein the following condition is satisfied. When the refractive power at the d-line of the first b lens group is Φ1b and the refractive power at the d-line of the negative meniscus lens constituting the first b lens group is Φ1m, the following expression −1.0 <Φ1b / Φ1m <− 0.4
The photographic lens according to claim 1, wherein the following condition is satisfied. The refractive power at the d-line of the entire photographing lens system when focusing on a short distance object is Φn, and the refractive power at the d-line of the entire photographing lens system when focusing on an object at infinity is Φi, When the change in the distance between the first lens group and the second lens group when focusing from an object at infinity to a short distance object is ΔD, the following expression | (Φn−Φi) / ΔD | <0. 35
The photographic lens according to claim 1, wherein the following condition is satisfied.   An inspection apparatus comprising the photographing lens according to claim 1, wherein light from an object is imaged at a predetermined position.

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